Not Applicable.
Not Applicable.
1. Field of Invention
This invention relates to apparatus and method for assistance in determining the safe advisory speed for roadways.
2. Prior Art
The safe and comfortable speed for traverse of a curve in a highway often is indicated by a sign mounted at the beginning of the curve which states the advisory speed for traverse of the curve. Such curves commonly are encountered as curves in two-lane roadways and on interconnecting ramps between roadways. Advisory speeds are dependent on roadway conditions, sight distance, intersections and driveways, accident history, and on the lateral horizontal acceleration experienced by the vehicle and occupants. Advisory speeds currently are determined using a ball-bank indicator or an electronic inclinometer, both of which indicate the lean or tilt of a vehicle while traversing the curve, and which are surrogates for lateral horizontal acceleration. Unfortunately, the measurement of lean or tilt is plagued with variables of the type of vehicle, in particular, in the suspension system and wheel base width. The invention of this application is an automatic device which determines and records the maximum lateral horizontal acceleration experienced by a vehicle and occupants traversing a curve. Acceleration data derived using the apparatus and methods of this invention are used to help determine the advisory speed for curves.
Elements which may affect the advisory speed for a curve include pavement conditions, operating speeds, vehicle suspension systems, roadway gradients, surface friction factors, vehicle classifications, vehicle occupancy and highway gravitational forces and human factors.
U.S. Pat. No. 2,831,266 discloses a tilt indicating apparatus in which an illuminated ball which moves in an arcuate tube indicates the amount of tilt of the apparatus.
U.S. Pat. No. 5,343,411 discloses an accelerometer built into a vehicle in which the acceleration or deceleration is integrated or differentiated and the result compared with a reference signal. If the observed signal exceeds a reference signal, an airbag is activated. This allows activation of the airbag only when a significant event occurs.
U.S. Pat. No. 4,357,594 discloses a vehicular hazard warning system which is responsive to, among other signals, abrupt deceleration. A microprocessor is used to relate the rate of deceleration with the blinking of warning lights.
U.S. Pat. No. 5,208,754 discloses a device for calculating estimated vehicle acceleration and speed. Vehicle speed is determined by two methods, from the wheel speed, and from acceleration as measured by an accelerometer. When, during acceleration, there is wheel slippage the accelerometer measurements are used in determining vehicle speed. At other times the vehicle speed is determined from wheel speed.
U.S. Pat. No. 5,617,086 discloses a traffic monitoring system which, among other things, monitors the passage of vehicles entering a curve and, using a microprocessor, calculates the safe speed for negotiating the curve, and indicates the safe speed on a sign. Inputs concerning the vehicles include vehicle height and weight. Sensors in the pavement detect the passage and speed of the vehicle.
U.S. Pat. No. 5,992,032 discloses a computer based inclinometer which uses the piezoelectric effect to measure the inclination of a plane with respect to a reference plane.
U.S. Pat. No. 6,121,873 discloses a device for measuring lateral acceleration rate of a vehicle body, among other things. The vehicle has sensors for the detection of the turn rate, an acceleration applied in a horizontal direction traverse to a longitudinal axis of the body, called the xe2x80x9ctraverse acceleration sensorxe2x80x9d, and the vehicle speed. Data from these sensors are used to determine the vehicle speed, yaw rate, lateral acceleration and roll rate. The lateral acceleration of the vehicle body at the yaw sensor is calculated as the product of yaw rate and vehicle speed. The turn rate sensor is mounted at the center of gravity and the lateral acceleration sensor is mounted above the yaw rate sensor. The data derived from these two sensors are used to calculate the roll rate. The output is the vehicle speed, yaw rate, lateral acceleration at the center of gravity, and the roll rate.
In a second embodiment, two traverse acceleration sensors located at the upper front and lower rear of the vehicle are used in the determination of yaw rate without using a sensor for the detection of the turn rate. Sensors for the vehicle speed, turn rate, and transverse acceleration are used in determination of the vehicle speed, yaw rate, traverse acceleration at the center of gravity, and roll rate. There is no recording of the maximum lateral horizontal acceleration.
The prior art systems do not disclose the characteristics of the present invention, that of determining and recording the maximum traverse acceleration during a discrete period of measurement. Furthermore, method of application of determined maximum traverse acceleration as one parameter in a determination of the safe advisory speed for a curve of the present invention.
The objective of the advisory speed meter of the present invention is to provide an apparatus for accurate, reproducible determination of maximum lateral horizontal acceleration in a vehicle for assistance in determining the safe advisory speed for a curve in a road way.
Another objective of the advisory speed meter of the present invention is to provide an apparatus for recording the maximum lateral horizontal acceleration experienced in a vehicle traversing a curve in a roadway.
Another objective of the advisory speed meter of the present invention is to provide an objective, reliable, reproducible, accurate method for determining the maximum lateral horizontal acceleration experienced in a vehicle traversing a curve in a roadway for use in determining the safe advisory speed for traversing the curve.
Another objective of the advisory speed meter of the present invention is to provide an apparatus for recording the maximum lateral horizontal acceleration experienced in a vehicle traversing a curve in a roadway which is inexpensive, easy to use, and may be manufactured and used without adverse effect on the environment.
The advisory speed meter is a meter for determining the maximum lateral horizontal acceleration experienced by the occupants of a vehicle and comprises an accelerometer unit capable of sensing the lateral horizontal acceleration experienced in a vehicle, the accelerometer unit mounted on the floor of the vehicle at the vehicle centerline, the front of the accelerometer unit oriented toward the front of the vehicle, the accelerometer unit mounted perpendicular to the vehicle floor, and a meter unit capable of calculating and displaying the maximum lateral horizontal acceleration experienced by a vehicle, the accelerometer unit connected by a connector to the meter unit.
The process for determining the advisory speed for a curve in a roadway comprises the steps of traversing the curve in a vehicle of specified type at a specified constant speed, measuring the maximum lateral horizontal acceleration experienced by the vehicle while traversing the curve using a vehicle accelerometer, repeating the traversing curve and measuring the maximum lateral horizontal acceleration steps at various speeds, determining the speed of traverse associated with a predetermined maximum lateral horizontal acceleration, and designating the speed of traverse associated with a predetermined maximum lateral horizontal acceleration as the advisory speed for the curve in the roadway.